Process for the electrostatic separation of the sylvite (kci) component of a mineral



United States Patent Int. Cl. B03b 1/04 US. Cl. 209-9 Claims ABSTRACT OFTHE DISCLOSURE A process for the electrostatic separation of mineralmixtures, and. particularly to conditioned particulate crude potassiumsalts and the electrostatic separation thereof. In particularembodiments of thepresent invention crude particulate potassium saltmixtures are treated with inorganic mineral acids or inorganic alkalinereacting substances before, during or after the particulate material istreated with organic conditioning agents, comprising anionic compoundswhich form negatively charged radicals that split 01? positive ions andthereby control the electrostatic charging of the particulate material.

CROSS-REFERENCES TO RELATED APPLICATIONS 'fApplicants claim priorityunder 35 U.S.C. 119 for application Ser. N0. K 58,696 filed Mar. 1,1966, in the-- Federal Republic of Germany.

BACKGROUND OF THE INVENTION It is known that minerals containing crudepotassium- 3,477,566 Patented Nov. 11, 1969 DESCRIPTION OF THE INVENTIONIt is therefore an object of the present invention to improve efficiencyand selectivity in the process of electrostatically separatingparticulate mineral mixtures.

Another object of the present invention is an improvement in theefficiency and selectivity of the electrostatic separation of crudepotassium salts having a particulate size less than 0.1 mm.

Still another object of the present invention is an improvement in theefliciency and selectivity of the electrostatic separation of crudepotassium salts containing impurities of clay.

Other objects of the present invention are improved coatings forparticulate mixtures of crude potassium salts which facilitate theelectrostatic separation thereof.

A particular object of the present invention is a particulate mixture ofcrude potassium salt having a coating comprising a mixture of an organicconditioning agent and an inorganic acid or base.

Another particular object of the present invention is a particulatemixture of crude potassium salt that is treated with an inorganic acidor base followed by a treatment with an anionic organic conditioningagent. Still another particular object of the present invention is aparticulate mixture of crude potassium salt that is treated with ananionic organic conditioning agent followed by a treatment with aninorganic acid or base.

A further particular object of the present invention is a' particulatemixture of crude potassium salt that is treated with an anionic organicconditioning agent followed by treatment with gaseous hydrogen chlorideor ammonia.

Upon further study of the specification and claims other objects andadvantages of the present invention will become apparent.

' According to the present invention it has been found salts andmanyfother mineralfniixtures 'can be separated into their componentselectrostatically after being preconditioned, especially by organiccompounds which by forming negatively charged radicals split off oneor'rnore protons or metal ions. By a suitable choice of conditioningagent, or by a combination of different conditioning agents, theelectrostatic charging of the different mineral components can becontrolled-so that multiple-component' systems are separated completelywith high yield into individual mineral components of greater purity.

These prior art methods, conditioning agents and starting materials arefully set forth in German Patents 1,056,551, 1,061,713, 1,076,593, and1,102,663, and the corresponding US. Patent 3,217,876, the disclosuresof which are incorporated herein.

Autenrieth discloses in US. Patent 3,217,876 conditioning agents and therecycling and reconditioning of a portion of the particulate saltmixture.

The conditioning agents disclosed in the prior art patents are suitablefor use in the present invention.

It is postulated that the conditioning does not depend,

like a flotation process, on a selective application of the conditioningagent to the mineral components. On the contrary, the conditioning forelectrostatic separation is made without selectivity. The selectivedistribution of electric charges to the individual minerals isdecisively favored according to the specificity ofthe-particular-mineral bythe application of the conditioning agent tothe surfaceof the powdered mineral mixture. "The efiiciency of the priorart processes is somewhat limited by the presence of claylike componentsand the selectivity falls off in the smallest particle range of lessthan 0.1 mm.

that the specific distribution of electric charges between the mineralsto be electrostatically separated is greatly improved when the powderedmixture, either before, during or after treatment with a prior artconditioning agent, is also treated with very small amounts of inorganicmineral acids, or in other cases with inorganic alkaline reactingsubstances, preferably NaOH, KOH, or NH OH. Even with mineral mixturesthat are difficult to process, itis possible with the present inventionto give them strong and highly selective charges. The unfavorable effectof claylike components, which limited the prior art processes, is to alarge extent acoided thereby while at the same time the selectivity inthe smallest particle range of less than 0.1 mm. diameter isconsiderably increased. The acids or bases which are used as additionalreagents are applied advantageously as dilute or concentrated solutionsin water, but are also added to the mineral mixture in their gaseous orsolid state and thoroughly mixed therewith. The most suitable reagent,its most suitable concentration and the best method of adding it, dependlargely on theproperties of the mineral mixture to be processed and areeasily determined by those skilled in the art. 1

The electrostatic separation of the present invention is advantageouslycarried out with ground or pulverized particulate mineral crudes such assylvinite and hartsalz or mixtures thereof with the separation of saltssuch as sylvite, kierserite, rock salt and halite.

Representative examples of the organic conditioning agents suitable forconditioning the sy'lvite containing crude ,salts or mixtures of thosecrude salts prior to the separation steps are among others:

3 (1) Mixtures of fatty acids C C or of parts thereof, for

instance (a) Mixtures of fatty acids C -C (b) Mixtures of fatty acids CC (c) Mixtures of fatty acids C C (d) Mixtures of fatty acids C C (e)Mixtures of fatty acids 014-022 (2) Linseed oil fatty acids; (3) Benzoicacid; (4) Phenylacetic acid; 10 (5) Salicylic acid; (6) Phthalic acid;(7) Alpha-nitroso-beta-naphthol, and salts of the above organic acids;(8) Nonyl sulfate; (9) Sodium salt of alkylsulfonic acid; (10) Sodiumsalt of oxystearic sulfonic acid;

be construed as merely illustrative, and not limitative of the remainderof the specification and claims in any way whatsoever.

Example 1 Crude material: Hartsalz with a K 0 content of 12.9%.

Conditioning agent: a first run fatty acid mixture having 6-12 C-atoms.

The hartsalz is ground to a fineness of less than 1.0 mm. and is firstconditioned and mixed by spraying upon it 0.2 g./ kg. of a mixture of,e.g. first run fatty acids having about 612 C-atoms and is then warmedto 65 C. by a current of warm air and separated into its components byfalling through a potential gradient of 4 kv./cm. in a freefallelectrostatic separator. Instead of the first run fatty acids, otherprior art conditioning agents are used, as suggested for example by theGerman and United States patents disclosed in the Background of theInvention.

TABLE I Percent K10 Percent K 0 Percent K 0 in 1st in 2nd ConditioningAgent in residue concentrate concentrate 0.2 gJkg. of first run fattyacid mixture.. 2. 5 25. 2 4 1. 0

(11) Sodium salt of benzylnaphthalenesulfonic acid; (12) Sulfonatedamides of fatty acids; (13) Sodium salt of oxystearinsulfonicacid+sodium salt of alkylsulfonic acid 1:1; (14) Sodium salt ofoxystearic sulfonic acid-l-sodium salt of ricinic acid 1:1; (15)Beta-nitroso-alpha-naphthol and mixtures of 1 to 15. Preferred examplesof the inorganic acids used in the Further runs were then performed inwhich the crude salt after being conditioned with the first run fattyacid mixture was then mixed with 0.5 ml. of two normal acids per kg. ofcrude salt. After this second mixing the salt was warmed to 65 C. anddried by a current of warm air and then separated into its components inthe same manner as disclosed above, in a free-fall separator by apotential gradient of 4 kv./ cm. The results are given in Table II.

TABLE II Percent K 0 Percent K 0 Percent K 0 in Is in 2nd ConditioningAgent in residue concentrate concentrate 0.2 g./kg. first run fattyacid- Plus 0.5 mL/kg. 2 N HCl 1. 1 40. 6 64. 0 Plus 0.5 nil/kg. 2 N H504. 1. 1 39.3 51. 1 Plus 0.5 ml./kg. HNOa.-. 1. 3 34. 2 48. 9 Plus 0.5mL/kg. H1304-.." 0. 0 38. 2 50. 8 Plus 0.5 ml./kg. 2 N colloidal silicicacid suspended in H 0... 1. 6 36. 0 51. 0

present invention are HCl in aqueous or gaseous form, H 80 HNO H PO andcolloidal silicic acid suspended in water.

The inorganic bases preferably used in the present invention are aqueousor gaseous NH NaOH or KOH.

Combinations of mineral mixtures with a conditioning agent and aninorganic acid which particularly illustrate the new and unexpectedresults of the invention are hartsalz having in terms of K 0, 12.9%treated with 6 to 12 carbon atom fatty acid and HCl, H I-INO H PO 50 orcolloidal silicic acid; and hartsalz having about 12-13% K 0 and 3% claytreated with 3 to 12 carbon atom fatty acid mixture, salicylic acid,phenylacetic acid, phthalic acid, or nitroso-beta-naphthol and HCl, H 80HNO or H3PO4.

Illustrations of combinations of mineral mixtures with a conditioningagent and an inorganic base showing the new and unexpected results ofthe present invention include sylvinite having in terms of K 0, 18.5%and 5% clay treated with 6 to 12 carbon fatty acid and NaOH, KOH, NHOI-I or NH and sylvinite having 1516% K 0 and about 2% clay with 3 to 12carbon fatty acid, salicylic acid, benzoic acid or phthalic acid andNaOH, KOH or NH OH.

The procedures and conditions for crushing the mineral mixture, applyingthe conditioning agent and carrying out the electrostatic separation arefully disclosed in U.S. Patents 3,217,876 and 3,225,924.

Before separation in the electrostatic field the preconditioned saltsare preferably heated to temperatures be- 7 tween about 30 and 90 C.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The following preferred specific embodiments are,therefore, to

A comparison of the results of the results with and without thesubsequent acid treatment shows the extraordinary improvement in theseparating process. Whereas without the subsequent treatment with acidsolutions the residues contained about 2.5% K 0, the residues after acidtreatment contained only 0.9 to 1.6% K 0. The improvement is shown evenmore clearly by the concentrates. After the subsequent acid treatmentsthe K 0 concentrations were 10-15% higher in the first separation stagethan without such acid treatment, and in the second separation stagethey were also 1015% higher. After such acid treatment the highestconcentrates (by which is meant the end products of concentration aftertwo or more concentrating stages) show an exceptionally high degree ofpurity. Whereas without acid treatment it is possible in the presentcase to obtain a maximum concentration of only 52% K 0 yield of 88%,after the acid treatment a maximum concentration of more than 60% K 0with a total K 0 yield of 92% or more was obtained.

As Table III shows, the selectivity in the fine granular range that isdiffcult to process is greatly improved by the acid treatment.

TABLE III Selectivity of electrostatic separation in granule size rangesup to 0.1 mm.

1 Percent K 0 in the highest concentrate.

The results listed in Table IV show that the crude salts that wereseparated as illustrated in Tables II and III may r. i have the processmodified by subjecting the salts to the Conditioning agent: First runfatty acid mixture havacid treatment before as well as after theirconditioning ing 612 C-atoms. treatment with the usual conditioningagents,.and.a1so in. The. crude salt isground to 1.0 mm. granule sizeand is admixture with the conditioning agents. first sprayed in with 0.2g. of a mixture of first run fatty 5 acids having 6-12 C-atoms per kg.of crude salt, and then TABLE IV without. subsequent conditioning iswarmed to 60 C. by a .current of warmairand is then separated by apotential 1 gradient of 4 kv./cm. in a free-fall separator. The sepa-Treatment with the acid before, edema;

tion of the first run fatty acids or the like. 'j p rated products arelisted in Table VI.

' TABLE I Percent K20 Percent K20 Percent K20 in 1st in 2nd Conditioningagent in residue concentrate concentrate 0.2 g. first run fatty acid perlrg. crude salt 4. 7 25. 1 30. 5

Percent K 0 Percent K o in in residue 1st concentrate The high K 0content in the residue and also the meagre Conditioning with mineralacid: enrichment of it in the concentrates show that this is not B to22:; 20 a good processing method. After I 1.1 39.4

TABLE VII Percent K20 Percent K20 I Percent K in 1st in 2nd ConditioningAgent 7 in residue concentrate concentrate 0.2 g. first run fatty acidmixture per kg. crude salt-- Plus 0.5 ml. 2 N NaOH per kg. crudesalt- 1. 9 38 49 Plus 0.5 ml. 2 N KOH per kg. crude salt..- 1. 9 38. 850.1 Plus 0.5 ml. 2 N NH4OH per kg. crude salt 1. 6 40. 5 52. 3 Plus0.017 grams gaseous NH; per kg. crude salt added to the drying air 1. 5t2. 0 54. 0

Thevalues given in Table V show that the results de- In Table VII aregiven the results of subsequent treatpend primarily on the amount ofpure acid with which the ment with diluted alkalies, aqueous ammonia orgaseous crude salt is treated, and that the concentration of the acidammonia added to the drying air, of the crude salt that is of onlylittle importance. has been preconditioned with the fatty acids. In eachIn the separation runs listed in Table V the acid con- 35 case there wasa definite improvement in the processing. centrations ranged from 4 N togaseous, water-freeHCl. The K 0 contents of the residues are now onlyabout /5 It is of importance only that the absolute amount of acid ashigh as without the use of alkalies as ancillary conis kept at anoptimum value, such as can easily be deterditioning agents. The K 0contents of the concentrates mined by one skilled in the art. are about-25% higher. TABLE v V Percent K Percent'K O 7 Percent K20 in 1st in 2ndConditioning Agent v inresidne concentrate concentrate 0.2 g./kg. firstrun fatty acid- Plus 0.25 ml. 4 N HCL. 1. 0 41. 0 55. 1 Plus 0.125 ml. 8N HCL 1. 2 42. 3 55. 0 1. 1 41. 5 54. 3

Plus 0.99 ml. 12 N nor- Example 2 Examples 3a to 3e As previously setforth in the specification, applicants *Crude material: Hartsalz with a.K 0 content of 12- have found that in somecases the treatment withinorganic 13 and 3 clay. bases is preferred to the treatment withinorganic acid. -Separation temperature: C.

TABLE VIII K20 yield Percent K20 (content of in 2nd raw material OrgamcConditioning agent Inorganic acid concentrate equals 100%) (a) Fattyacid mixture of 0 -01; atoms, 0.2 g./kg 41.0 88 Do 56.8 94.8 Do-.- 55.195.4 Do-.- 54.0 95.1 Do-.- 51.1 94.9 Do 50.8 94.6 (b) salicylic acid,0.2 2 Ike 45. 3 88. 2 Do 53. 5 95. 5 D0 54.1 93.4 (c) Phenylacetlc acid,0.2 g./kg 46. 5 85. 6 Do 55.3 93.3 Do.-.. 45.7 95.2 1) Phthahc acid, 0.2gJ g. 45. 1 s5. 2 D 57.3 94. 5 Do..... 55.8 94.1 (e) Nitroso- 46.0 83. 1Do--. 53.4 95.1 Do 52.9 94.8

It is here shown that treatment with alkalics as ancillary conditioningagents results in a desired improvement. E l 4 4d As an example of this,the electrostatic processing of a clay-rich sylvinite: Crude material:Sylvrnrte with a K 0 content of 15 Raw material: Sylvinite with a K 0content of 18.5% 16% and about 2% clay. having about 5% clay. Separationtemperature: 45 C.

TABLE IX Exploited K20 of Percent K10 the crude in 2nd salt con- OrganicConditioning agent Inorganic Base concentrate taining K10 (a) Fatty eaidmixture of -01:, 0.2 g./kg 30. 79. 7 Do 2 m1.lkg.1 N NH4OH 56.8 95.7./kg. 1 N NHiOH 57. 1 96. 0 50. 1 94. l 52. 0 94. 7 46. 7 85. 3 56. 394. 7 55. 8 94. 0 46. 3 86. 3 55. 3 95. 0 55. 1 94. 8 47. 1 85. 8 58. 893. 2 56. 8 94. 1

The preceding examples can be repeated with similar success bysubstituting the generically and specifically described reactants andoperating conditions of this invention for those used in the precedingexamples.

We claim:

1. In a process for electrostatic separation of sylvite containing crudesalt mineral, the improvement comprising: contacting saidmineral, aftergrinding, with a small amount of an agent selected from the groupconsisting of a small amount of aqueous HCl, aqueous H SO aqueous H POaqueous NaOH, aqueous KOH, aqueous NH OH, a suspension of silicic acidin water, gaseous NH or gaseous HCl and additionally conditioning saidmineral with organic conditioning agents containing an anionic organicradical and warming up said mineral in a stream of hot drying gas andsubjecting said mineral to electrostatic separation of its components.

2. The electrostatic separation process of claim 1, wherein said agentis selected from the group consisting of aqueous suspensions andsolutions of inorganic hydroxides.

3. The electrostatic separation process of claim 1, wherein saidinorganic acids and bases are selected from the group consisting ofabout 200-2000 ml. of about 1.0 to 4 normal HCl, about 200-2000 ml. ofabout 1.0 to 4 normal H 80 about 200-2000 ml. of about 1.0 to 4 normalHNO about 200-2000 ml. of about 1.0 to 4 normal colloidal silicic acidsuspended in water, about 200-2000 ml. of about 1.0 to 4 normal NaOH,about 200-2000 ml. of about 1.0 to 4 normal KO'H, about 200- 2000 ml. ofabout 1.0 to 4 normal NH OH, about 5-25 g. gaseous NH or about 5-25 g.HCl per ton salt mineral.

4. The process according to claim 3, wherein said inorganic agents andsaid anionic conditioning agents simultaneously or after mixing withsaid ground salt mineral are warmed up with hot gas at temperaturesbetween about 30-90 C.

5. The electrostatic separation process of claim 3, wherein saidinorganic acids and bases are selected from the group consisting ofabout 500-2000 ml. of about 1-2 normal HCl, about 500-2000 ml. of about1-2 normal H 50 about 500 ml. of about 2 normal colloidal silicic acidsuspended in water, about 500-2000 ml. of about 1-2 normal NaOH, about500-2000 ml. of about 1-2 normal KOH, about 500-2000 ml. of about 1-2normal NH OH, about 5-25 g. gaseous NH per ton salt mineral, or about5-25 g. gaseous HCl per ton salt mineral, and said salt mineral isconditioned with a small quantity of about 200 g. of an organic anionicconditioning agent per ton salt mineral.

References Cited UNITED STATES PATENTS 2,090,418 8/ 1937 Johnson 209-1272,188,932 2/1940 Weinig 209167 X 2,593,431 4/1952 Fraas 2099 3,008,57311/ 1961 Gross 2099 3,049,233 8/ 1962 Marullo 209l66 3,388,794 6/ 1968Peuschel 209--9 FOREIGN PATENTS 650,049 10/ 1962 Canada. 1,108,632 6/1961 Germany.

HARRY B. THORNTON, Primary Examiner R. HALPER, Assistant Examiner U.S.Cl. X.R. 209-127

